Zoom Lens System, Imaging Device and Camera

ABSTRACT

A zoom lens system comprising: a positive first lens unit; a negative second lens unit; a positive third lens unit; a fourth lens unit; and an aperture diaphragm provided between the third lens unit and the fourth lens unit, wherein in zooming, the first to third lens units are moved along an optical axis to perform magnification change, the third lens unit includes two or more lens elements and one or more inter-lens-element air spaces, and the conditions: −7.0&lt;f 1 /f 2 &lt;−4.0 and f T /f W &gt;9.0 (f 1  and f 2 : composite focal lengths of the first and second lens units, f W  and f T : focal lengths of the entire system at a wide-angle limit and a telephoto limit) are satisfied.

BACKGROUND

1. Field

The present disclosure relates to zoom lens systems, imaging devices and cameras.

2. Description of the Related Art

Cameras including an image sensor for performing photoelectric conversion, such as digital still cameras and digital video cameras, have been required to have high resolution, and particularly in recent years, these cameras have been strongly required to have a reduced thickness, a high zooming ratio, and capability of compensating various aberrations. For example, various kinds of zoom lens systems have been proposed, each having a three-or-more unit configuration of positive, negative, and positive, or positive, negative, and negative, in which a first lens unit having positive optical power, a second lens unit having negative optical power, a third lens unit having positive or negative optical power, and a subsequent lens unit are arranged in order from an object side to an image side. Hereinafter, the cameras including an image sensor for performing photoelectric conversion, such as digital still cameras and digital video cameras, are simply referred to as “digital cameras”.

Japanese Laid-Open Patent Publications Nos. 2010-237455, 2007-108398, and H10-111455 each disclose a zoom lens having the three-or-more unit configuration of positive, negative, and positive.

Japanese Laid-Open Patent Publication No. 2009-265652 discloses a zoom lens system having the three-or-more unit configuration of positive, negative, and positive, or positive, negative, and negative.

Japanese Laid-Open Patent Publication No. 2009-175736 discloses a zoom lens having the three-or-more unit configuration of positive, negative, and positive, or positive, negative, and negative.

Japanese Laid-Open Patent Publication No. 2009-009121 discloses a zoom lens system having the three-or-more unit configuration of positive, negative, and positive.

SUMMARY

The present disclosure provides: a high-performance and thin zoom lens system that has, as well as high resolution, a high zooming ratio, but has less aberration fluctuation in zooming; an imaging device employing the zoom lens system; and a thin and compact camera employing the imaging device.

The novel concepts disclosed herein were achieved in order to solve the foregoing problems in the related art, and herein is disclosed:

a zoom lens system, in order from an object side to an image side, comprising:

a first lens unit having positive optical power;

a second lens unit having negative optical power;

a third lens unit having positive optical power;

a fourth lens unit having optical power; and

an aperture diaphragm provided between the third lens unit and the fourth lens unit, wherein

in zooming from a wide-angle limit to a telephoto limit at the time of image taking, the first lens unit, the second lens unit, and the third lens unit are moved along an optical axis to perform magnification change,

the third lens unit includes two or more lens elements, and one or more inter-lens-element air spaces, and

the following conditions (1) and (a) are satisfied:

−7.0<f ₁ /f ₂<−4.0  (1)

f _(T) /f _(W)>9.0  (a)

where,

f₁ is a composite focal length of the first lens unit,

f₂ is a composite focal length of the second lens unit,

f_(W) is a focal length of the entire system at a wide-angle limit, and

f_(T) is a focal length of the entire system at a telephoto limit.

The novel concepts disclosed herein were achieved in order to solve the foregoing problems in the related art, and herein is disclosed:

an imaging device capable of outputting an optical image of an object as an electric image signal, comprising:

a zoom lens system that forms the optical image of the object; and

an image sensor that converts the optical image formed by the zoom lens system into the electric image signal, wherein

the zoom lens system is a zoom lens system, in order from an object side to an image side, comprising:

a first lens unit having positive optical power;

a second lens unit having negative optical power;

a third lens unit having positive optical power;

a fourth lens unit having optical power; and

an aperture diaphragm provided between the third lens unit and the fourth lens unit, wherein

in zooming from a wide-angle limit to a telephoto limit at the time of image taking, the first lens unit, the second lens unit, and the third lens unit are moved along an optical axis to perform magnification change,

the third lens unit includes two or more lens elements, and one or more inter-lens-element air spaces, and

the following conditions (1) and (a) are satisfied:

−7.0<f ₁ /f ₂<−4.0  (1)

f _(T) /f _(W)>9.0  (a)

where,

f₁ is a composite focal length of the first lens unit,

f₂ is a composite focal length of the second lens unit,

f_(W) is a focal length of the entire system at a wide-angle limit, and

f_(T) is a focal length of the entire system at a telephoto limit.

The novel concepts disclosed herein were achieved in order to solve the foregoing problems in the related art, and herein is disclosed:

a camera for converting an optical image of an object into an electric image signal, and performing at least one of displaying and storing of the converted image signal, comprising:

an imaging device including a zoom lens system that forms the optical image of the object, and an image sensor that converts the optical image formed by the zoom lens system into the electric image signal, wherein

the zoom lens system is a zoom lens system, in order from an object side to an image side, comprising:

a first lens unit having positive optical power;

a second lens unit having negative optical power;

a third lens unit having positive optical power;

a fourth lens unit having optical power; and

an aperture diaphragm provided between the third lens unit and the fourth lens unit, wherein

in zooming from a wide-angle limit to a telephoto limit at the time of image taking, the first lens unit, the second lens unit, and the third lens unit are moved along an optical axis to perform magnification change,

the third lens unit includes two or more lens elements, and one or more inter-lens-element air spaces, and

the following conditions (1) and (a) are satisfied:

−7.0<f ₁ /f ₂<−4.0  (1)

f _(T) /f _(W)>9.0  (a)

where,

f₁ is a composite focal length of the first lens unit,

f₂ is a composite focal length of the second lens unit,

f_(W) is a focal length of the entire system at a wide-angle limit, and

f_(T) is a focal length of the entire system at a telephoto limit.

A zoom lens system in the present disclosure is a high-performance and thin zoom lens system that has, as well as high resolution, a high zooming ratio, but has less aberration fluctuation in zooming. An imaging device in the present disclosure employs the zoom lens system, and a camera employing the imaging device is thin and compact.

BRIEF DESCRIPTION OF THE DRAWINGS

This and other objects and features of the present disclosure will become clear from the following description, taken in conjunction with the exemplary embodiments with reference to the accompanied drawings in which:

FIG. 1 is a lens arrangement diagram showing an infinity in-focus condition of a zoom lens system according to Embodiment 1 (Numerical Example 1);

FIG. 2 is a longitudinal aberration diagram of an infinity in-focus condition of a zoom lens system according to Numerical Example 1;

FIG. 3 is a lateral aberration diagram of a zoom lens system according to Numerical Example 1 at a telephoto limit in a basic state where image blur compensation is not performed and in an image blur compensation state;

FIG. 4 is a lens arrangement diagram showing an infinity in-focus condition of a zoom lens system according to Embodiment 2 (Numerical Example 2);

FIG. 5 is a longitudinal aberration diagram of an infinity in-focus condition of a zoom lens system according to Numerical Example 2;

FIG. 6 is a lateral aberration diagram of a zoom lens system according to Numerical Example 2 at a telephoto limit in a basic state where image blur compensation is not performed and in an image blur compensation state;

FIG. 7 is a lens arrangement diagram showing an infinity in-focus condition of a zoom lens system according to Embodiment 3 (Numerical Example 3);

FIG. 8 is a longitudinal aberration diagram of an infinity in-focus condition of a zoom lens system according to Numerical Example 3;

FIG. 9 is a lateral aberration diagram of a zoom lens system according to Numerical Example 3 at a telephoto limit in a basic state where image blur compensation is not performed and in an image blur compensation state;

FIG. 10 is a lens arrangement diagram showing an infinity in-focus condition of a zoom lens system according to Embodiment 4 (Numerical Example 4);

FIG. 11 is a longitudinal aberration diagram of an infinity in-focus condition of a zoom lens system according to Numerical Example 4;

FIG. 12 is a lateral aberration diagram of a zoom lens system according to Numerical Example 4 at a telephoto limit in a basic state where image blur compensation is not performed and in an image blur compensation state;

FIG. 13 is a lens arrangement diagram showing an infinity in-focus condition of a zoom lens system according to Embodiment 5 (Numerical Example 5);

FIG. 14 is a longitudinal aberration diagram of an infinity in-focus condition of a zoom lens system according to Numerical Example 5;

FIG. 15 is a lateral aberration diagram of a zoom lens system according to Numerical Example 5 at a telephoto limit in a basic state where image blur compensation is not performed and in an image blur compensation state; and

FIG. 16 is a schematic configuration diagram of a digital still camera according to Embodiment 6.

DETAILED DESCRIPTION

Hereinafter, embodiments will be described with reference to the drawings as appropriate. However, descriptions more detailed than necessary may be omitted. For example, detailed description of already well known matters or description of substantially identical configurations may be omitted. This is intended to avoid redundancy in the description below, and to facilitate understanding of those skilled in the art.

It should be noted that the applicant provides the attached drawings and the following description so that those skilled in the art can fully understand this disclosure. Therefore, the drawings and description are not intended to limit the subject defined by the claims.

Embodiments 1 to 5

FIGS. 1, 4, 7, 10 and 13 are lens arrangement diagrams of zoom lens systems according to Embodiments 1 to 5, respectively.

Each of FIGS. 1, 4, 7, 10 and 13 shows a zoom lens system in an infinity in-focus condition. In each Fig., part (a) shows a lens configuration at a wide-angle limit, part (b) shows a lens configuration at a middle position, and part (c) shows a lens configuration at a telephoto limit. The wide-angle limit is the minimum focal length condition, and the focal length is expressed by f_(W). The middle position is an intermediate focal length condition, and the focal length is expressed by f_(M)=√(f_(W)*f_(T)). The telephoto limit is the maximum focal length condition, and the focal length is expressed by f_(T). Further, in each Fig., each bent arrow provided between part (a) and part (b) indicates a line obtained by connecting the positions of each lens unit at a wide-angle limit, a middle position and a telephoto limit in order from the top. Accordingly, in the part between the wide-angle limit and the middle position, and the part between the middle position and the telephoto limit, the positions are connected simply with a straight line, and this line does not indicate an actual motion of each lens unit. Furthermore, in each Fig., an arrow imparted to a lens unit indicates focusing from an infinity in-focus condition to a close-object in-focus condition. That is, in FIGS. 1, 4, 7 and 13, the arrow indicates the direction in which a fourth lens unit G4 described later moves in focusing from the infinity in-focus condition to the close-object in-focus condition. In FIG. 10, the arrow indicates the direction in which a fifth lens unit G5 described later moves in focusing from the infinity in-focus condition to the close-object in-focus condition.

Each of the zoom lens systems according to Embodiments 1 to 4, in order from the object side to the image side, comprises: a first lens unit G1 having positive optical power; a second lens unit G2 having negative optical power; a third lens unit G3 having positive optical power; a fourth lens unit G4 having negative optical power; and a fifth lens unit G5 having positive optical power. The zoom lens system according to Embodiment 5, in order from the object side to the image side, comprises: a first lens unit G1 having positive optical power; a second lens unit G2 having negative optical power; a third lens unit G3 having positive optical power; and a fourth lens unit G4 having positive optical power.

In the zoom lens systems according to Embodiments 1 to 3, in zooming, the first lens unit G1, the second lens unit G2, the third lens unit G3, and the fourth lens unit G4 move in a direction along the optical axis such that the intervals between the respective lens units, that is, the interval between the first lens unit G1 and the second lens unit G2, the interval between the second lens unit G2 and the third lens unit G3, the interval between the third lens unit G3 and the fourth lens unit G4, and the interval between the fourth lens unit G4 and the fifth lens unit G5 vary. In the zoom lens system according to Embodiment 4, in zooming, all of the lens units move in the direction along the optical axis such that the intervals between the respective lens units, that is, the interval between the first lens unit G1 and the second lens unit G2, the interval between the second lens unit G2 and the third lens unit G3, the interval between the third lens unit G3 and the fourth lens unit G4, and the interval between the fourth lens unit G4 and the fifth lens unit G5 vary. In the zoom lens system according to Embodiment 5, in zooming, all of the lens units move in the direction along the optical axis such that the intervals between the respective lens units, that is, the interval between the first lens unit G1 and the second lens unit G2, the interval between the second lens unit G2 and the third lens unit G3, and the interval between the third lens unit G3 and the fourth lens unit G4 vary. In the zoom lens system according to each embodiment, by arranging the lens units in a desired optical power configuration, size reduction in the entire lens system is achieved while maintaining high optical performance.

In FIGS. 1, 4, 7, 10 and 13, an asterisk “*” imparted to a particular surface indicates that the surface is aspheric. In each Fig., symbol (+) or (−) imparted to the symbol of each lens unit corresponds to the sign of the optical power of the lens unit. In each Fig., the straight line located on the most right-hand side indicates the position of the image surface S. On the object side relative to the image surface S, i.e., between the image surface S and the most image side lens surface in the fifth lens unit G5 in FIGS. 1, 4, 7 and 10, or between the image surface S and the most image side lens surface in the fourth lens unit G4 in FIG. 13, a plane parallel plate P equivalent to an optical low-pass filter or a face plate of an image sensor is provided.

Embodiment 1

As shown in FIG. 1, the first lens unit G1, in order from the object side to the image side, comprises: a negative meniscus first lens element L1 with the convex surface facing the object side; a positive meniscus second lens element L2 with the convex surface facing the object side; and a positive meniscus third lens element L3 with the convex surface facing the object side. Among these, the first lens element L1 and the second lens element L2 are cemented with each other. In the surface data of the corresponding Numerical Example described later, surface number 2 is imparted to an adhesive layer between the first lens element L1 and the second lens element L2.

The second lens unit G2, in order from the object side to the image side, comprises: a negative meniscus fourth lens element L4 with the convex surface facing the object side; a negative meniscus fifth lens element L5 with the convex surface facing the image side; and a bi-convex sixth lens element L6. Among these, the fourth lens element L4 has two aspheric surfaces.

The third lens unit G3, in order from the object side to the image side, comprises: a bi-convex seventh lens element L7; a bi-convex eighth lens element L8, a bi-concave ninth lens element L9; and a bi-convex tenth lens element L10. Among these, the eighth lens element L8 and the ninth lens element L9 are cemented with each other. In the surface data of the corresponding Numerical Example described later, surface number 16 is imparted to an adhesive layer between the eighth lens element L8 and the ninth lens element L9. The seventh lens element L7 has two aspheric surfaces.

The fourth lens unit G4 comprises solely a negative meniscus eleventh lens element L11 with the convex surface facing the object side.

The fifth lens unit G5 comprises solely a bi-convex twelfth lens element L12. The twelfth lens element L12 has two aspheric surfaces.

In the zoom lens system according to Embodiment 1, an aperture diaphragm A is provided between the third lens unit G3 and the fourth lens unit G4. In zooming from a wide-angle limit to a telephoto limit at the time of image taking, the aperture diaphragm A moves along the optical axis to the object side, integrally with the third lens unit G3.

In the zoom lens system according to Embodiment 1, a plane parallel plate P is provided on the object side relative to the image surface S, i.e., between the image surface S and the twelfth lens element L12.

In the zoom lens system according to Embodiment 1, in zooming from a wide-angle limit to a telephoto limit at the time of image taking, the first lens unit G1 and the fourth lens unit G4 move nearly monotonically to the object side, the second lens unit G2 moves to the image side with locus of a convex to the image side, the third lens unit G3 moves monotonically to the object side, and the fifth lens unit G5 is fixed with respect to the image surface S. That is, in zooming, the first lens unit G1, the second lens unit G2, the third lens unit G3, and the fourth lens unit G4 move along the optical axis such that the interval between the first lens unit G1 and the second lens unit G2 increases, the interval between the second lens unit G2 and the third lens unit G3 decreases, the interval between the third lens unit G3 and the fourth lens unit G4 changes, and the interval between the fourth lens unit G4 and the fifth lens unit G5 increases.

In the zoom lens system according to Embodiment 1, in focusing from an infinity in-focus condition to a close-object in-focus condition, the fourth lens unit G4 moves along the optical axis to the image side.

Embodiment 2

As shown in FIG. 4, the first lens unit G1, in order from the object side to the image side, comprises: a negative meniscus first lens element L1 with the convex surface facing the object side; a positive meniscus second lens element L2 with the convex surface facing the object side; and a positive meniscus third lens element L3 with the convex surface facing the object side. Among these, the first lens element L1 and the second lens element L2 are cemented with each other. In the surface data of the corresponding Numerical Example described later, surface number 2 is imparted to an adhesive layer between the first lens element L1 and the second lens element L2.

The second lens unit G2, in order from the object side to the image side, comprises: a negative meniscus fourth lens element L4 with the convex surface facing the object side; a bi-concave fifth lens element L5; and a bi-convex sixth lens element L6. Among these, the fourth lens element L4 has two aspheric surfaces.

The third lens unit G3, in order from the object side to the image side, comprises: a bi-convex seventh lens element L7; a positive meniscus eighth lens element L8 with the convex surface facing the object side; a negative meniscus ninth lens element L9 with the convex surface facing the object side; and a bi-convex tenth lens element L10. Among these, the eighth lens element L8 and the ninth lens element L9 are cemented with each other. In the surface data of the corresponding Numerical Example described later, surface number 16 is imparted to an adhesive layer between the eighth lens element L8 and the ninth lens element L9. The seventh lens element L7 has two aspheric surfaces.

The fourth lens unit G4 comprises solely a negative meniscus eleventh lens element L11 with the convex surface facing the object side.

The fifth lens unit G5 comprises solely a bi-convex twelfth lens element L12. The twelfth lens element L12 has two aspheric surfaces.

In the zoom lens system according to Embodiment 2, an aperture diaphragm A is provided between the third lens unit G3 and the fourth lens unit G4. In zooming from a wide-angle limit to a telephoto limit at the time of image taking, the aperture diaphragm A moves along the optical axis to the object side, integrally with the third lens unit G3.

In the zoom lens system according to Embodiment 2, a plane parallel plate P is provided on the object side relative to the image surface S, i.e., between the image surface S and the twelfth lens element L12.

In the zoom lens system according to Embodiment 2, in zooming from a wide-angle limit to a telephoto limit at the time of image taking, the first lens unit G1 moves to the object side with locus of a convex to the image side, the second lens unit G2 moves to the image side with locus of a convex to the image side, the third lens unit G3 moves nearly monotonically to the object side, the fourth lens unit G4 moves monotonically to the object side, and the fifth lens unit G5 is fixed with respect to the image surface S. That is, in zooming, the first lens unit G1, the second lens unit G2, the third lens unit G3, and the fourth lens unit G4 move along the optical axis such that the interval between the first lens unit G1 and the second lens unit G2 increases, the interval between the second lens unit G2 and the third lens unit G3 decreases, the interval between the third lens unit G3 and the fourth lens unit G4 changes, and the interval between the fourth lens unit G4 and the fifth lens unit G5 increases.

In the zoom lens system according to Embodiment 2, in focusing from an infinity in-focus condition to a close-object in-focus condition, the fourth lens unit G4 moves along the optical axis to the image side.

Embodiment 3

As shown in FIG. 7, the first lens unit G1, in order from the object side to the image side, comprises: a negative meniscus first lens element L1 with the convex surface facing the object side; a bi-convex second lens element L2; and a positive meniscus third lens element L3 with the convex surface facing the object side. Among these, the first lens element L1 and the second lens element L2 are cemented with each other. In the surface data of the corresponding Numerical Example described later, surface number 2 is imparted to an adhesive layer between the first lens element L1 and the second lens element L2.

The second lens unit G2, in order from the object side to the image side, comprises: a negative meniscus fourth lens element L4 with the convex surface facing the object side; a negative meniscus fifth lens element L5 with the convex surface facing the image side; and a bi-convex sixth lens element L6. Among these, the fourth lens element L4 has two aspheric surfaces.

The third lens unit G3, in order from the object side to the image side, comprises: a bi-convex seventh lens element L7; a positive meniscus eighth lens element L8 with the convex surface facing the object side; a negative meniscus ninth lens element L9 with the convex surface facing the object side; and a bi-convex tenth lens element L10. Among these, the eighth lens element L8 and the ninth lens element L9 are cemented with each other. In the surface data of the corresponding Numerical Example described later, surface number 16 is imparted to an adhesive layer between the eighth lens element L8 and the ninth lens element L9. The seventh lens element L7 has two aspheric surfaces.

The fourth lens unit G4 comprises solely a negative meniscus eleventh lens element L11 with the convex surface facing the object side.

The fifth lens unit G5 comprises solely a bi-convex twelfth lens element L12. The twelfth lens element L12 has two aspheric surfaces.

In the zoom lens system according to Embodiment 3, an aperture diaphragm A is provided between the third lens unit G3 and the fourth lens unit G4. In zooming from a wide-angle limit to a telephoto limit at the time of image taking, the aperture diaphragm A moves along the optical axis to the object side, integrally with the third lens unit G3.

In the zoom lens system according to Embodiment 3, a plane parallel plate P is provided on the object side relative to the image surface S, i.e., between the image surface S and the twelfth lens element L12.

In the zoom lens system according to Embodiment 3, in zooming from a wide-angle limit to a telephoto limit at the time of image taking, the first lens unit G1 moves nearly monotonically to the object side, the second lens unit G2 moves to the image side with locus of a convex to the image side, the third lens unit G3 moves monotonically to the object side, the fourth lens unit G4 moves to the object side with locus of a convex to the image side, and the fifth lens unit G5 is fixed with respect to the image surface S. That is, in zooming, the first lens unit G1, the second lens unit G2, the third lens unit G3, and the fourth lens unit G4 move along the optical axis such that the interval between the first lens unit G1 and the second lens unit G2 increases, the interval between the second lens unit G2 and the third lens unit G3 decreases, the interval between the third lens unit G3 and the fourth lens unit G4 changes, and the interval between the fourth lens unit G4 and the fifth lens unit G5 increases.

In the zoom lens system according to Embodiment 3, in focusing from an infinity in-focus condition to a close-object in-focus condition, the fourth lens unit G4 moves along the optical axis to the image side.

Embodiment 4

As shown in FIG. 10, the first lens unit G1, in order from the object side to the image side, comprises: a negative meniscus first lens element L1 with the convex surface facing the object side; a positive meniscus second lens element L2 with the convex surface facing the object side; and a positive meniscus third lens element L3 with the convex surface facing the object side. Among these, the first lens element L1 and the second lens element L2 are cemented with each other. In the surface data of the corresponding Numerical Example described later, surface number 2 is imparted to an adhesive layer between the first lens element L1 and the second lens element L2.

The second lens unit G2, in order from the object side to the image side, comprises: a negative meniscus fourth lens element L4 with the convex surface facing the object side; a bi-concave fifth lens element L5; and a bi-convex sixth lens element L6. Among these, the fourth lens element L4 has two aspheric surfaces, and the fifth lens element L5 has an aspheric object side surface.

The third lens unit G3, in order from the object side to the image side, comprises: a bi-convex seventh lens element L7; a bi-convex eighth lens element L8; and a bi-concave ninth lens element L9. Among these, the eighth lens element L8 and the ninth lens element L9 are cemented with each other. In the surface data of the corresponding Numerical Example described later, surface number 16 is imparted to an adhesive layer between the eighth lens element L8 and the ninth lens element L9. The seventh lens element L7 has two aspheric surfaces, and the ninth lens element L9 has an aspheric image side surface.

The fourth lens unit G4 comprises solely a negative meniscus tenth lens element L10 with the convex surface facing the object side. The tenth lens element L10 has an aspheric object side surface.

The fifth lens unit G5 comprises solely a bi-convex eleventh lens element L11. The eleventh lens element L11 has two aspheric surfaces.

In the zoom lens system according to Embodiment 4, an aperture diaphragm A is provided between the third lens unit G3 and the fourth lens unit G4. In zooming from a wide-angle limit to a telephoto limit at the time of image taking, the aperture diaphragm A moves along the optical axis to the object side, integrally with the third lens unit G3.

In the zoom lens system according to Embodiment 4, a plane parallel plate P is provided on the object side relative to the image surface S, i.e., between the image surface S and the eleventh lens element L11.

In the zoom lens system according to Embodiment 4, in zooming from a wide-angle limit to a telephoto limit at the time of image taking, the first lens unit G1 and the third lens unit G3 move nearly monotonically to the object side, the second lens unit G2 and the fifth lens unit G5 move nearly monotonically to the image side, and the fourth lens unit G4 moves slightly to the object side. That is, in zooming, the first lens unit G1, the second lens unit G2, the third lens unit G3, the fourth lens unit G4, and the fifth lens unit G5 move along the optical axis such that the interval between the first lens unit G1 and the second lens unit G2 increases, the interval between the second lens unit G2 and the third lens unit G3 decreases, the interval between the third lens unit G3 and the fourth lens unit G4 increases, and the interval between the fourth lens unit G4 and the fifth lens unit G5 changes.

In the zoom lens system according to Embodiment 4, in focusing from an infinity in-focus condition to a close-object in-focus condition, the fifth lens unit G5 moves along the optical axis to the object side.

Embodiment 5

As shown in FIG. 13, the first lens unit G1, in order from the object side to the image side, comprises: a negative meniscus first lens element L1 with the convex surface facing the object side; a bi-convex second lens element L2; and a positive meniscus third lens element L3 with the convex surface facing the object side. Among these, the first lens element L1 and the second lens element L2 are cemented with each other. In the surface data of the corresponding Numerical Example described later, surface number 2 is imparted to an adhesive layer between the first lens element L1 and the second lens element L2.

The second lens unit G2, in order from the object side to the image side, comprises: a negative meniscus fourth lens element L4 with the convex surface facing the object side; a bi-concave fifth lens element L5; and a positive meniscus sixth lens element L6 with the convex surface facing the object side.

The third lens unit G3, in order from the object side to the image side, comprises: a bi-convex seventh lens element L7; a bi-convex eighth lens element L8; and a bi-concave ninth lens element L9. Among these, the eighth lens element L8 and the ninth lens element L9 are cemented with each other. In the surface data of the corresponding Numerical Example described later, surface number 16 is imparted to an adhesive layer between the eighth lens element L8 and the ninth lens element L9. The eighth lens element L8 has an aspheric object side surface.

The fourth lens unit G4 comprises solely a positive meniscus tenth lens element L10 with the convex surface facing the object side. The tenth lens element L10 has two aspheric surfaces.

In the zoom lens system according to Embodiment 5, an aperture diaphragm A is provided between the third lens unit G3 and the fourth lens unit G4. In zooming from a wide-angle limit to a telephoto limit at the time of image taking, the aperture diaphragm A moves along the optical axis to the object side, integrally with the third lens unit G3.

In the zoom lens system according to Embodiment 5, a plane parallel plate P is provided on the object side relative to the image surface S, i.e., between the image surface S and the tenth lens element L10.

In the zoom lens system according to Embodiment 5, in zooming from a wide-angle limit to a telephoto limit at the time of image taking, the first lens unit G1 and the third lens unit G3 move nearly monotonically to the object side, the second lens unit G2 moves nearly monotonically to the image side, and the fourth lens unit G4 moves to the image side with locus of a convex to the object side. That is, in zooming, the first lens unit G1, the second lens unit G2, the third lens unit G3, and the fourth lens unit G4 move along the optical axis such that the interval between the first lens unit G1 and the second lens unit G2 increases, the interval between the second lens unit G2 and the third lens unit G3 decreases, and the interval between the third lens unit G3 and the fourth lens unit G4 changes.

In the zoom lens system according to Embodiment 5, in focusing from an infinity in-focus condition to a close-object in-focus condition, the fourth lens unit G4 moves along the optical axis to the object side.

In the zoom lens systems according to Embodiments 1 to 5, the aperture diaphragm A is provided between the third lens unit G3 and the fourth lens unit G4. In zooming from a wide-angle limit to a telephoto limit at the time of image taking, the aperture diaphragm A moves along the optical axis, integrally with the third lens unit G3. Therefore, it is possible to reduce the size of the entire lens system while maintaining high optical performance.

In the zoom lens systems according to Embodiments 1 to 5, the third lens unit G3 includes two or more lens elements, and one or more inter-lens-element air spaces. Therefore, it is possible to successfully compensate aberrations, and it is possible to reduce the size of the entire lens system while maintaining high optical performance and having a high zooming ratio.

In the zoom lens systems according to Embodiments 1 to 5, since the fourth lens unit G4 is composed of one lens element, reduction in the size of the entire lens system is achieved. Further, in the zoom lens systems according to Embodiments 1 to 3 and 5, rapid focusing from an infinity in-focus condition to a close-object in-focus condition is easily achieved.

In the zoom lens systems according to Embodiments 1 to 4, since the fifth lens unit G5 is composed of one lens element, reduction in the size of the entire lens system is achieved. Further, in the zoom lens system according to Embodiment 4, rapid focusing from an infinity in-focus condition to a close-object in-focus condition is easily achieved.

In the zoom lens systems according to Embodiments 1 to 5, in focusing from an infinity in-focus condition to a close-object in-focus condition, the fourth lens unit G4 or the fifth lens unit G5 moves along the optical axis. Therefore, high optical performance can be maintained even in the close-object in-focus condition.

The zoom lens systems according to Embodiments 1 to 4 each have a five-unit configuration, and the zoom lens system according to Embodiment 5 has a four-unit configuration. However, the number of lens units constituting each lens system is not particularly limited as long as it is not less than four. Further, the optical powers of the fourth lens unit G4 and the lens units located on the image side relative to the fourth lens unit G4 are not particularly limited.

Any lens unit among the first to fifth lens units G1 to G5 or a sub lens unit corresponding to a part of each lens unit in the zoom lens systems according to Embodiments 1 to 4, or any lens units among the first to fourth lens units G1 to G4 or a sub lens unit corresponding to a part of each lens unit in the zoom lens system according to Embodiment 5, may be moved in a direction perpendicular to the optical axis. Thereby, movement of an image point caused by vibration of the entire system can be compensated, that is, image blur caused by hand blurring, vibration and the like can be optically compensated.

When compensating the movement of the image point caused by vibration of the entire system, for example, the third lens unit G3 may be moved in the direction perpendicular to the optical axis. Thereby, image blur can be compensated in a state that size increase in the entire zoom lens system is suppressed to realize a compact configuration and that excellent imaging characteristics such as small decentering coma aberration and small decentering astigmatism are satisfied.

In a case where a lens unit is composed of a plurality of lens elements, the above-mentioned sub lens unit corresponding to a part of each lens unit indicates any one lens element or a plurality of adjacent lens elements among the plurality of lens elements.

As described above, Embodiments 1 to 5 have been described as examples of art disclosed in the present application. However, the art in the present disclosure is not limited to these embodiments. It is understood that various modifications, replacements, additions, omissions, and the like have been performed in these embodiments to give optional embodiments, and the art in the present disclosure can be applied to the optional embodiments.

The following description is given for conditions to be satisfied by a zoom lens system like the zoom lens systems according to Embodiments 1 to 5. Here, a plurality of beneficial conditions is set forth for the zoom lens system according to each embodiment. A construction that satisfies all the plural conditions is most beneficial for the zoom lens system. However, when an individual condition is satisfied, a zoom lens system having the corresponding effect is obtained.

For example, in a zoom lens system, like the zoom lens systems according to Embodiments 1 to 5, which, in order from the object side to the image side, comprises: a first lens unit having positive optical power; a second lens unit having negative optical power; a third lens unit having positive optical power; a fourth lens unit having optical power; and an aperture diaphragm provided between the third lens unit and the fourth lens unit, wherein, in zooming from a wide-angle limit to a telephoto limit at the time of image taking, the first lens unit, the second lens unit, and the third lens unit are moved along an optical axis to perform magnification change, and the third lens unit includes two or more lens elements, and one or more inter-lens-element air spaces, the following conditions (1) and (a) are satisfied. Hereinafter, the lens configuration of this zoom lens system is referred to as a basic configuration of the embodiment.

−7.0<f ₁ /f ₂<−4.0  (1)

f _(T) /f _(W)>9.0  (a)

where,

f₁ is a composite focal length of the first lens unit,

f₂ is a composite focal length of the second lens unit,

f_(W) is a focal length of the entire system at a wide-angle limit, and

f_(T) is a focal length of the entire system at a telephoto limit.

The condition (a) sets forth the ratio between the focal length of the entire system at a wide-angle limit and the focal length of the entire system at a telephoto limit. The zoom lens system having the basic configuration satisfies the condition (a), and therefore, has a high zooming ratio, and ensures high magnification.

The condition (1) sets forth the ratio between the focal length of the first lens unit and the focal length of the second lens unit. When the value goes below the lower limit of the condition (1), the focal length of the second lens unit becomes excessively short, and aberration fluctuation at the time of magnification change increases, which causes difficulty in compensating aberrations. Further, the focal length of the first lens unit becomes excessively long, and the amount of movement of the first lens unit, which is desired for securing high magnification, becomes excessively great, which causes difficulty in providing compact lens barrels, imaging devices, and cameras. When the value exceeds the upper limit of the condition (1), the focal length of the first lens unit becomes excessively short, and aberration fluctuation at the time of magnification change increases, which causes difficulty in compensating aberrations. In addition, the diameter of the first lens unit increases, which causes difficulty in providing compact lens barrels, imaging devices, and cameras. Further, error sensitivity to inclination of the first lens unit becomes excessively high, which may cause difficulty in assembling optical systems.

It is beneficial that the condition (1) is satisfied under the following condition (a)′.

f _(T) /f _(W)>13.0  (a)′

For example, in a zoom lens system having the basic configuration like the zoom lens systems according to Embodiments 1 to 5, it is beneficial that the following condition (2) is satisfied.

0.5<|f ₁ /f ₄|<4.2  (2)

where,

f₁ is a composite focal length of the first lens unit, and

f₄ is a composite focal length of the fourth lens unit.

The condition (2) sets forth the ratio between the focal length of the first lens unit and the focal length of the fourth lens unit. When the value goes below the lower limit of the condition (2), the focal length of the fourth lens unit becomes excessively long, and the amount of movement of the fourth lens unit becomes excessively great, which causes difficulty in providing compact lens barrels, imaging devices, and cameras. Further, the focal length of the first lens unit becomes excessively short, and aberration fluctuation at the time of magnification change increases, which causes difficulty in compensating aberrations. In addition, the diameter of the first lens unit increases, which causes difficulty in providing compact lens barrels, imaging devices, and cameras. Further, error sensitivity to inclination of the first lens unit becomes excessively high, which may cause difficulty in assembling optical systems. When the value exceeds the upper limit of the condition (2), the focal length of the first lens unit becomes excessively long, and the amount of movement of the first lens unit, which is desired for securing high magnification, becomes excessively great, which causes difficulty in providing compact lens barrels, imaging devices, and cameras.

When at least one of the following conditions (2)′ and (2)″ is satisfied, the above-mentioned effect is achieved more successfully.

1.5<|f ₁ /f ₄|  (2)′

|f ₁ /f ₄|<3.0  (2)″

It is beneficial that the conditions (2), (2)′, and (2)″ are satisfied under the above condition (a)′.

For example, in a zoom lens system having the basic configuration like the zoom lens systems according to Embodiments 1 to 5, it is beneficial that the following condition (3) is satisfied.

0.8<L _(T) /f _(T)<1.4  (3)

where,

L_(T) is an overall length of lens system (a distance from a most object side surface of the first lens unit to an image surface) at a telephoto limit, and

f_(T) is a focal length of the entire system at a telephoto limit.

The condition (3) sets forth the ratio between the overall length of lens system at a telephoto limit and the focal length of the entire system at a telephoto limit. When the value goes below the lower limit of the condition (3), the overall length of lens system at a telephoto limit becomes excessively short, and the focal length of each lens unit becomes excessively short. Thereby, aberration fluctuation at the time of magnification change increases, which causes difficulty in compensating aberrations. When the value exceeds the upper limit of the condition (3), the overall length of lens system at a telephoto limit becomes excessively long, which causes difficulty in providing compact lens barrels, imaging devices, and cameras.

When at least one of the following conditions (3)′ and (3)″ is satisfied, the above-mentioned effect is achieved more successfully.

0.9<L _(T) /f _(T)  (3)′

L _(T) /f _(T)<1.2  (3)″

It is beneficial that the conditions (3), (3)′, and (3)″ are satisfied under the above condition (a)′.

Each of the lens units constituting the zoom lens systems according to Embodiments 1 to 5 is composed exclusively of refractive type lens elements that deflect the incident light by refraction, i.e., lens elements of a type in which deflection is achieved at the interface between media each having a distinct refractive index. However, the present disclosure is not limited to this. For example, the lens units may employ diffractive type lens elements that deflect the incident light by diffraction; refractive-diffractive hybrid type lens elements that deflect the incident light by a combination of diffraction and refraction; or gradient index type lens elements that deflect the incident light by distribution of refractive index in the medium. In particular, in the refractive-diffractive hybrid type lens elements, when a diffraction structure is formed in the interface between media having mutually different refractive indices, wavelength dependence in the diffraction efficiency is improved. Thus, such a configuration is beneficial.

Moreover, in each embodiment, a configuration has been described that on the object side relative to the image surface S, i.e., between the image surface S and the most image side lens surface of the fifth lens unit G5 in Embodiments 1 to 4, or between the image surface S and the most image side lens surface of the fourth lens unit G4 in Embodiment 5, a plane parallel plate P such as an optical low-pass filter and a face plate of an image sensor is provided. This low-pass filter may be: a birefringent type low-pass filter made of, for example, a crystal whose predetermined crystal orientation is adjusted; or a phase type low-pass filter that achieves desired characteristics of optical cut-off frequency by diffraction.

Embodiment 6

FIG. 16 is a schematic configuration diagram of a digital still camera according to Embodiment 6. In FIG. 16, the digital still camera comprises: an imaging device having a zoom lens system 1 and an image sensor 2 that is a CCD; a liquid crystal display monitor 3; and a body 4. A zoom lens system according to Embodiment 1 is employed as the zoom lens system 1. In FIG. 16, the zoom lens system 1 comprises a first lens unit G1, a second lens unit G2, a third lens unit G3, an aperture diaphragm A, a fourth lens unit G4, and a fifth lens unit G5. In the body 4, the zoom lens system 1 is arranged on the front side, and the image sensor 2 is arranged on the rear side of the zoom lens system 1. On the rear side of the body 4, the liquid crystal display monitor 3 is arranged, and an optical image of a photographic object generated by the zoom lens system 1 is formed on an image surface S.

A lens barrel comprises a main barrel 5, a moving barrel 6, and a cylindrical cam 7. When the cylindrical cam 7 is rotated, the first lens unit G1, the second lens unit G2, the third lens unit G3 and the aperture diaphragm A, the fourth lens unit G4, and the fifth lens unit G5 move to predetermined positions relative to the image sensor 2, so that zooming from a wide-angle limit to a telephoto limit is achieved. The fourth lens unit G4 is movable in the optical axis direction by a motor for focus adjustment.

As such, when the zoom lens system according to Embodiment 1 is employed in a digital still camera, a small digital still camera can be obtained that has a high resolution and high capability of compensating curvature of field and that has a short overall length of lens system at the time of non-use. In the digital still camera shown in FIG. 16, any one of the zoom lens systems according to Embodiments 2 to 5 may be employed in place of the zoom lens system according to Embodiment 1. Further, the optical system of the digital still camera shown in FIG. 16 is applicable also to a digital video camera for moving images. In this case, moving images with high resolution can be acquired in addition to still images.

The digital still camera according to Embodiment 6 has been described for a case that the employed zoom lens system 1 is any one of the zoom lens systems according to Embodiments 1 to 5. However, in these zoom lens systems, the entire zooming range need not be used. That is, in accordance with a desired zooming range, a range where satisfactory optical performance is obtained may exclusively be used. Then, the zoom lens system may be used as one having a lower magnification than the zoom lens system described in Embodiments 1 to 5.

Further, Embodiment 6 has been described for a case that the zoom lens system is applied to a lens barrel of so-called barrel retraction construction. However, the present invention is not limited to this. For example, the zoom lens system may be applied to a lens barrel of so-called bending configuration where a prism having an internal reflective surface or a front surface reflective mirror is arranged at an arbitrary position within the first lens unit G1 or the like. Further, in Embodiment 6, the zoom lens system may be applied to a so-called sliding lens barrel in which a part of the lens units constituting the zoom lens system like the entirety of the second lens unit G2, the entirety of the third lens unit G3, or alternatively a part of the second lens unit G2 or the third lens unit G3 is caused to escape from the optical axis at the time of barrel retraction.

An imaging device comprising any one of the zoom lens systems according to Embodiments 1 to 5, and an image sensor such as a CCD or a CMOS may be applied to a mobile terminal device such as a smart-phone, a Personal Digital Assistance, a surveillance camera in a surveillance system, a Web camera, a vehicle-mounted camera or the like.

As described above, Embodiment 6 has been described as an example of art disclosed in the present application. However, the art in the present disclosure is not limited to this embodiment. It is understood that various modifications, replacements, additions, omissions, and the like have been performed in this embodiment to give optional embodiments, and the art in the present disclosure can be applied to the optional embodiments.

Numerical examples are described below in which the zoom lens systems according to Embodiments 1 to 5 are implemented. In the numerical examples, the units of the length in the tables are all “mm”, while the units of the view angle in the tables are all “°”. In the numerical examples, r is the radius of curvature, d is the axial distance, nd is the refractive index to the d-line, and vd is the Abbe number to the d-line. In the numerical examples, the surfaces marked with * are aspheric surfaces, and the aspheric surface configuration is defined by the following expression.

$Z = {\frac{h^{2}/r}{1 + \sqrt{1 - {\left( {1 + \kappa} \right)\left( {h/r} \right)^{2}}}} + {A\; 4h^{4}} + {A\; 6h^{6}} + {A\; 8h^{8}} + {A\; 10h^{10}} + {A\; 12h^{12}} + {A\; 14h^{14}}}$

Here, κ is the conic constant, A4, A6, A8, A10, A12 and A14 are a fourth-order, sixth-order, eighth-order, tenth-order, twelfth-order and fourteenth-order aspherical coefficients, respectively.

FIGS. 2, 5, 8, 11 and 14 are longitudinal aberration diagrams of the zoom lens systems according to Numerical Examples 1 to 5, respectively.

In each longitudinal aberration diagram, part (a) shows the aberration at a wide-angle limit, part (b) shows the aberration at a middle position, and part (c) shows the aberration at a telephoto limit. Each longitudinal aberration diagram, in order from the left-hand side, shows the spherical aberration, the astigmatism and the distortion. In each Fig., the spherical aberration is indicated as “SA(mm)”, the astigmatism is indicated as “AST(mm)”, and the distortion is indicated as “DIS(%)”. In each spherical aberration diagram, the vertical axis indicates the F-number, and the solid line, the short dash line and the long dash line indicate the characteristics to the d-line having a wavelength of 587.56 nm, the F-line having a wavelength of 486.13 nm and the C-line having a wavelength of 656.28 nm, respectively. In each astigmatism diagram, the vertical axis indicates the image height, and the solid line and the dash line indicate the characteristics to the sagittal plane and the meridional plane, respectively. In each distortion diagram, the vertical axis indicates the image height. In each Fig., the F-number is indicated as “F”, the image height is indicated as “H”, the sagittal plane is indicated as “s”, and the meridional plane is indicated as “m”.

FIGS. 3, 6, 9, 12 and 15 are lateral aberration diagrams of the zoom lens systems at a telephoto limit according to Numerical Examples 1 to 5, respectively.

In each lateral aberration diagram, the aberration diagrams in the upper three parts correspond to a basic state where image blur compensation is not performed at a telephoto limit, while the aberration diagrams in the lower three parts correspond to an image blur compensation state where the entirety of the third lens unit G3 is moved by a predetermined amount in a direction perpendicular to the optical axis at a telephoto limit. Among the lateral aberration diagrams of a basic state, the upper part shows the lateral aberration at an image point of 70% of the maximum image height, the middle part shows the lateral aberration at the axial image point, and the lower part shows the lateral aberration at an image point of −70% of the maximum image height. Among the lateral aberration diagrams of an image blur compensation state, the upper part shows the lateral aberration at an image point of 70% of the maximum image height, the middle part shows the lateral aberration at the axial image point, and the lower part shows the lateral aberration at an image point of −70% of the maximum image height. In each lateral aberration diagram, the horizontal axis indicates the distance from the principal ray on the pupil surface, and the solid line, the short dash line and the long dash line indicate the characteristics to the d-line, the F-line and the C-line, respectively. In each lateral aberration diagram, the meridional plane is adopted as the plane containing the optical axis of the first lens unit G1 and the optical axis of the third lens unit G3.

In the zoom lens system according to each of the numerical examples, the amount of movement of the third lens unit G3 in a direction perpendicular to the optical axis in an image blur compensation state at a telephoto limit is as follows.

Numerical Example 1 0.094 mm Numerical Example 2 0.082 mm Numerical Example 3 0.105 mm Numerical Example 4 0.125 mm Numerical Example 5 0.197 mm

Here, when the shooting distance is infinity, at a telephoto limit, the amount of image decentering in a case that the zoom lens system inclines by 0.3° is equal to the amount of image decentering in a case that the entirety of the third lens unit G3 moves in parallel by each of the above-mentioned values in a direction perpendicular to the optical axis.

As seen from the lateral aberration diagrams, satisfactory symmetry is obtained in the lateral aberration at the axial image point. Further, when the lateral aberration at the +70% image point and the lateral aberration at the −70% image point are compared with each other in a basic state, all have a small degree of curvature and almost the same inclination in the aberration curve. Thus, decentering coma aberration and decentering astigmatism are small. This indicates that sufficient imaging performance is obtained even in an image blur compensation state. Further, when the image blur compensation angle of a zoom lens system is the same, the amount of parallel movement desired for image blur compensation decreases with decreasing focal length of the entire zoom lens system. Thus, at arbitrary zoom positions, sufficient image blur compensation can be performed for image blur compensation angles up to 0.3° without degrading the imaging characteristics.

Numerical Example 1

The zoom lens system of Numerical Example 1 corresponds to Embodiment 1 shown in FIG. 1. Table 1 shows the surface data of the zoom lens system of Numerical Example 1. Table 2 shows the aspherical data. Table 3 shows various data.

TABLE 1 (Surface data) Surface number r d nd vd Object surface ∞  1 39.12230 0.75000 1.84666 23.8  2 24.34130 0.01000 1.56732 42.8  3 24.34130 2.57250 1.49700 81.6  4 669.01800 0.15000  5 24.12950 1.79680 1.72916 54.7  6 79.16250 Variable  7* 40.41520 0.50000 1.87702 37.0  8* 4.92640 3.70580  9 −8.33810 0.30000 1.72916 54.7 10 −88.01810 0.22870 11 27.63010 1.21460 1.94595 18.0 12 −34.07630 Variable 13* 5.61650 2.15450 1.58332 59.1 14* −22.78570 0.50340 15 8.07340 1.26250 1.49700 81.6 16 −490.35460 0.01000 1.56732 42.8 17 −490.35460 0.30000 1.90366 31.3 18 4.81270 0.35810 19 12.15960 1.20290 1.52996 55.8 20 −11.64830 0.40000 21(Diaphragm) ∞ Variable 22 30.16120 0.50000 1.88300 40.8 23 8.20900 Variable 24* 9.68560 2.23030 1.52996 55.8 25* −93.78700 2.36430 26 ∞ 0.78000 1.51680 64.2 27 ∞ (BF) Image surface ∞

TABLE 2 (Aspherical data) Surface No. 7 K = 0.00000E+00, A4 = −5.63481E−04, A6 = 3.11555E−05, A8 = −8.17750E−07 A10 = 8.06105E−09, A12 = 0.00000E+00 Surface No. 8 K = 0.00000E+00, A4 = −8.76674E−04, A6 = −1.12420E−05, A8 = 2.70324E−06 A10 = −1.33807E−07, A12 = 0.00000E+00 Surface No. 13 K = 0.00000E+00, A4 = −7.29201E−04, A6 = −1.17969E−05, A8 = −6.10823E−06 A10 = 6.74583E−07, A12 = −4.48240E−08 Surface No. 14 K = 0.00000E+00, A4 = 8.59168E−05, A6 = −2.47587E−05, A8 = −1.87567E−06 A10 = 1.46231E−07, A12 = −2.05601E−08 Surface No. 24 K = 0.00000E+00, A4 = −6.47588E−04, A6 = 8.67198E−05, A8 = −5.62682E−06 A10 = 1.93110E−07, A12 = −4.72323E−09 Surface No. 25 K = 0.00000E+00, A4 = −7.33472E−04, A6 = 3.89493E−05, A8 = −1.04425E−06 A10 = −4.32516E−08, A12 = 0.00000E+00

TABLE 3 (Various data) Zooming ratio 14.71263 Wide-angle Middle Telephoto limit position limit Focal length 4.4482 17.0693 65.4446 F-number 3.44055 4.49104 6.16167 View angle 45.0718 12.6331 3.4043 Image height 3.7000 3.9000 3.9000 Overall length 46.3632 51.3938 62.4654 of lens system BF 0.48241 0.50874 0.45483 d6 0.3000 10.7372 21.3604 d12 16.7953 5.1183 0.3000 d21 3.4276 9.1186 10.4391 d23 2.0635 2.6166 6.6167 Entrance pupil 11.0268 35.9621 125.0203 position Exit pupil −11.4186 −20.0329 −54.5925 position Front principal 13.8124 38.8475 112.6593 points position Back principal 41.9150 34.3246 −2.9791 points position Single lens data Lens Initial surface element number Focal length 1 1 −77.9069 2 3 50.7587 3 5 46.9551 4 7 −6.4393 5 9 −12.6519 6 11 16.2860 7 13 7.9466 8 15 15.9947 9 17 −5.2725 10 19 11.4258 11 22 −12.9111 12 24 16.6900 Zoom lens unit data Initial Overall Lens surface Focal length of Front principal Back principal unit No. length lens unit points position points position 1 1 36.28987 5.27930 1.15149 3.09442 2 7 −5.85194 5.94910 0.35671 1.13559 3 13 9.23453 6.19140 −0.30820 1.47404 4 22 −12.91111 0.50000 0.36877 0.60037 5 24 16.68996 5.37460 0.13748 1.16482 Magnification of zoom lens unit Lens Initial Wide-angle Middle Telephoto unit surface No. limit position limit 1 1 0.00000 0.00000 0.00000 2 7 −0.21205 −0.34104 −0.89535 3 13 −0.48200 −1.12114 −1.38610 4 22 1.66825 1.71504 2.01678 5 24 0.71886 0.71728 0.72051

Numerical Example 2

The zoom lens system of Numerical Example 2 corresponds to Embodiment 2 shown in FIG. 4. Table 4 shows the surface data of the zoom lens system of Numerical Example 2. Table 5 shows the aspherical data. Table 6 shows various data.

TABLE 4 (Surface data) Surface number r d nd vd Object surface ∞  1 31.08320 0.75000 1.84666 23.8  2 20.54660 0.01000 1.56732 42.8  3 20.54660 2.64550 1.49700 81.6  4 152.85880 0.15000  5 24.63830 1.66280 1.72916 54.7  6 107.30480 Variable  7* 49.15490 0.50000 1.87702 37.0  8* 5.54240 3.71900  9 −10.64890 0.30000 1.72916 54.7 10 112.56090 0.22460 11 20.71430 1.29040 1.94595 18.0 12 −81.81860 Variable 13* 5.43680 1.87130 1.58332 59.1 14* −22.36220 0.40260 15 6.57880 1.45360 1.49700 81.6 16 46.91020 0.01000 1.56732 42.8 17 46.91020 0.30000 1.90366 31.3 18 4.17360 0.30410 19 7.92300 1.07350 1.52996 55.8 20 −15.71980 0.40000 21(Diaphragm) ∞ Variable 22 19.40140 0.50000 1.88300 40.8 23 5.56050 Variable 24* 9.90500 2.27410 1.52996 55.8 25* −84.49410 2.25770 26 ∞ 0.78000 1.51680 64.2 27 ∞ (BF) Image surface ∞

TABLE 5 (Aspherical data) Surface No. 7 K = 0.00000E+00, A4 = −6.82260E−04, A6 = 3.42662E−05, A8 = −7.06863E−07 A10 = 5.24073E−09, A12 = 0.00000E+00 Surface No. 8 K = 0.00000E+00, A4 = −8.55257E−04, A6 = −2.08462E−06, A8 = 2.57595E−06 A10 = −7.86710E−08, A12 = 0.00000E+00 Surface No. 13 K = 0.00000E+00, A4 = −7.38915E−04, A6 = 6.12372E−06, A8 = −7.45037E−06 A10 = 7.92758E−07, A12 = −5.22500E−08 Surface No. 14 K = 0.00000E+00, A4 = 1.71678E−04, A6 = 7.80329E−06, A8 = −4.99088E−06 A10 = 3.22395E−07, A12 = −2.42946E−08 Surface No. 24 K = 0.00000E+00, A4 = −4.14254E−04, A6 = 1.04417E−04, A8 = −5.96937E−06 A10 = 1.47200E−07, A12 = −3.27839E−09 Surface No. 25 K = 0.00000E+00, A4 = −8.50740E−04, A6 = 9.56957E−05, A8 = −5.15879E−06 A10 = 3.50417E−08, A12 = 0.00000E+00

TABLE 6 (Various data) Zooming ratio 11.03063 Wide-angle Middle Telephoto limit position limit Focal length 4.4498 14.8500 49.0837 F-number 3.44101 4.73422 6.16062 View angle 42.8989 14.5685 4.5571 Image height 3.5000 3.9000 3.9000 Overall length 47.2343 46.2180 52.9687 of lens system BF 0.48722 0.48685 0.45643 d6 0.3000 8.1432 17.4571 d12 19.1524 6.1570 0.3000 d21 1.6677 4.6342 6.6017 d23 2.7478 3.9176 5.2743 Entrance pupil 12.0384 30.0889 89.9355 position Exit pupil −10.1822 −16.6238 −24.5944 position Front principal 14.6324 32.0509 42.8463 points position Back principal 42.7846 31.3680 3.8850 points position Single lens data Lens Initial surface element number Focal length 1 1 −74.0055 2 3 47.4464 3 5 43.4920 4 7 −7.1611 5 9 −13.3284 6 11 17.5816 7 13 7.6883 8 15 15.2143 9 17 −5.0866 10 19 10.0990 11 22 −8.9793 12 24 16.8698 Zoom lens unit data Initial Overall Lens surface Focal length of Front principal Back principal unit No. length lens unit points position points position 1 1 33.79578 5.21830 1.12238 3.01496 2 7 −6.26139 6.03400 0.48676 1.44491 3 13 8.11525 5.81510 −0.43186 1.41460 4 22 −8.97929 0.50000 0.37862 0.60851 5 24 16.86977 5.31180 0.15727 1.19825 Magnification of zoom lens unit Lens Initial Wide-angle Middle Telephoto unit surface No. limit position limit 1 1 0.00000 0.00000 0.00000 2 7 −0.25511 −0.37491 −0.84760 3 13 −0.35202 −0.75087 −1.02588 4 22 2.01596 2.14616 2.29086 5 24 0.72728 0.72730 0.72910

Numerical Example 3

The zoom lens system of Numerical Example 3 corresponds to Embodiment 3 shown in FIG. 7. Table 7 shows the surface data of the zoom lens system of Numerical Example 3. Table 8 shows the aspherical data. Table 9 shows various data.

TABLE 7 (Surface data) Surface number r d nd vd Object surface ∞  1 57.54400 0.75000 1.84666 23.8  2 32.90100 0.01000 1.56732 42.8  3 32.90100 2.61090 1.49700 81.6  4 −118.20340 0.15000  5 24.21850 1.52590 1.72916 54.7  6 50.97680 Variable  7* 29.35900 0.50000 1.87702 37.0  8* 5.29960 4.05300  9 −7.89080 0.30000 1.72916 54.7 10 −60.13670 0.23680 11 41.52720 1.27550 1.94595 18.0 12 −26.55800 Variable 13* 6.06960 2.37110 1.58332 59.1 14* −23.88150 0.31890 15 7.14320 1.38840 1.49700 81.6 16 109.61190 0.01000 1.56732 42.8 17 109.61190 0.30000 1.90366 31.3 18 4.95430 0.45800 19 23.14400 1.09800 1.52996 55.8 20 −12.30130 0.40000 21(Diaphragm) ∞ Variable 22 30.20470 0.50000 1.88300 40.8 23 10.26950 Variable 24* 10.66430 2.04270 1.52996 55.8 25* −98.22820 2.84340 26 ∞ 0.78000 1.51680 64.2 27 ∞ (BF) Image surface ∞

TABLE 8 Aspherical data) Surface No. 7 K = 0.00000E+00, A4 = −7.15790E−04, A6 = 3.34579E−05, A8 = −6.64896E−07 A10 = 4.88846E−09, A12 = 0.00000E+00 Surface No. 8 K = 0.00000E+00, A4 = −9.90606E−04, A6 = −3.67284E−06, A8 = 1.95498E−06 A10 = −6.58573E−08, A12 = 0.00000E+00 Surface No. 13 K = 0.00000E+00, A4 = −6.16082E−04, A6 = −3.68104E−07, A8 = −5.75983E−06 A10 = 5.43157E−07, A12 = −2.72234E−08 Surface No. 14 K = 0.00000E+00, A4 = 1.78340E−05, A6 = −3.72044E−06, A8 = −4.60879E−06 A10 = 4.06332E−07, A12 = −2.11784E−08 Surface No. 24 K = 0.00000E+00, A4 = −1.08567E−03, A6 = 1.14745E−04, A8 = −6.05001E−06 A10 = 1.55891E−07, A12 = −2.89195E−09 Surface No. 25 K = 0.00000E+00, A4 = −1.36541E−03, A6 = 1.09701E−04, A8 = −4.19438E−06 A10 = 2.41875E−08, A12 = 0.00000E+00

TABLE 9 (Various data) Zooming ratio 16.47230 Wide-angle Middle Telephoto limit position limit Focal length 4.4501 18.0934 73.3027 F-number 3.44164 4.20219 6.16157 View angle 41.5033 11.9452 3.0330 Image height 3.4000 3.9000 3.9000 Overall length 49.0167 55.3864 70.1058 of lens system BF 0.49135 0.52241 0.45938 d6 0.3000 12.2557 24.4860 d12 18.5099 5.2649 0.3000 d21 3.6190 11.3314 12.4827 d23 2.1738 2.0894 8.4551 Entrance pupil 11.3371 38.4866 134.4812 position Exit pupil −12.3397 −22.9441 −128.8978 position Front principal 14.2438 42.6294 166.2455 points position Back principal 44.5666 37.2930 −3.1969 points position Single lens data Lens Initial surface element number Focal length 1 1 −92.0253 2 3 52.0843 3 5 61.7901 4 7 −7.4461 5 9 −12.4864 6 11 17.2815 7 13 8.5459 8 15 15.3058 9 17 −5.7498 10 19 15.3205 11 22 −17.8312 12 24 18.2708 Zoom lens unit data Initial Overall Lens surface Focal length of Front principal Back principal unit No. length lens unit points position points position 1 1 41.06452 5.04680 1.21748 3.07560 2 7 −6.41603 6.36530 0.48274 1.30249 3 13 10.09615 6.34440 −0.66695 1.36063 4 22 −17.83121 0.50000 0.40711 0.63842 5 24 18.27085 5.66610 0.13161 1.09620 Magnification of zoom lens unit Lens Initial Wide-angle Middle Telephoto unit surface No. limit position limit 1 1 0.00000 0.00000 0.00000 2 7 −0.20116 −0.32179 −0.83233 3 13 −0.49210 −1.25492 −1.58845 4 22 1.51412 1.51273 1.86297 5 24 0.72299 0.72129 0.72474

Numerical Example 4

The zoom lens system of Numerical Example 4 corresponds to Embodiment 4 shown in FIG. 10. Table 10 shows the surface data of the zoom lens system of Numerical Example 4. Table 11 shows the aspherical data. Table 12 shows various data.

TABLE 10 (Surface data) Surface number r d nd vd Object surface ∞  1 34.34930 0.65000 1.84666 23.8  2 21.47750 0.01000 1.56732 42.8  3 21.47750 2.03800 1.49700 81.6  4 147.07180 0.15000  5 26.49040 1.61860 1.77250 49.6  6 130.70190 Variable  7* 57.01000 0.30000 1.84973 40.6  8* 5.45040 3.07830  9* −17.37380 0.40000 1.77200 50.0 10 41.76440 0.15010 11 15.48890 1.19800 1.94595 18.0 12 −395.30340 Variable 13* 5.07260 1.87320 1.51776 69.9 14* −14.52160 0.29090 15 7.30900 1.14640 1.69680 55.5 16 −66.82490 0.01000 1.56732 42.8 17 −66.82490 0.30000 1.68400 31.3 18* 3.87590 0.50000 19(Diaphragm) ∞ Variable 20* 12.63810 0.50000 1.68400 31.3 21 8.93930 Variable 22* 26.96660 1.68640 1.58332 59.1 23* −17.12980 Variable 24 ∞ 0.78000 1.51680 64.2 25 ∞ (BF) Image surface ∞

TABLE 11 (Aspherical data) Surface No. 7 K = 0.00000E+00, A4 = −8.94401E−04, A6 = 6.21567E−05, A8 = −1.98151E−06 A10 = 2.99161E−08, A12 = −1.77821E−10, A14 = 0.00000E+00 Surface No. 8 K = 0.00000E+00, A4 = −1.06030E−03, A6 = 2.36965E−05, A8 = 1.64213E−06 A10 = −5.56501E−08, A12 = −1.14121E−09, A14 = 0.00000E+00 Surface No. 9 K = 0.00000E+00, A4 = 5.29698E−05, A6 = −3.68820E−06, A8 = 3.32156E−07 A10 = −6.16745E−09, A12 = 0.00000E+00, A14 = 0.00000E+00 Surface No. 13 K = 0.00000E+00, A4 = −7.42045E−04, A6 = −9.81495E−06, A8 = −1.14627E−05 A10 = 2.41648E−06, A12 = −2.74102E−07, A14 = 1.22994E−08 Surface No. 14 K = 0.00000E+00, A4 = 6.07823E−04, A6 = −6.47865E−05, A8 = 4.56339E−06 A10 = −2.28093E−07, A12 = −1.28148E−08, A14 = 3.13084E−09 Surface No. 18 K = 0.00000E+00, A4 = 1.90160E−04, A6 = 8.06372E−05, A8 = 5.02360E−06 A10 = −1.29991E−06, A12 = 0.00000E+00, A14 = 0.00000E+00 Surface No. 20 K = 0.00000E+00, A4 = −3.85673E−04, A6 = 1.93928E−05, A8 = −8.23950E−07 A10 = 4.98393E−09, A12 = 0.00000E+00, A14 = 0.00000E+00 Surface No. 22 K = 0.00000E+00, A4 = 1.33733E−03, A6 = −8.40850E−05, A8 = 5.21020E−06 A10 = −1.89946E−07, A12 = 2.92945E−09, A14 = 0.00000E+00 Surface No. 23 K = 0.00000E+00, A4 = 1.25012E−03, A6 = −9.34022E−05, A8 = 5.55813E−06 A10 = −2.00544E−07, A12 = 3.06426E−09, A14 = 0.00000E+00

TABLE 12 (Various data) Zooming ratio 9.39473 Wide-angle Middle Telephoto limit position limit Focal length 4.6466 14.2428 43.6536 F-number 3.08881 4.92645 5.98483 View angle 41.5422 15.0391 5.0055 Image height 3.6000 3.9000 3.9000 Overall length 42.4542 46.6111 55.6771 of lens system BF 0.77933 0.75151 0.73920 d6 0.3000 7.6536 17.9500 d12 16.4289 6.0700 0.9031 d19 1.0129 6.9323 10.8336 d21 2.4853 3.9951 5.9037 d23 4.7679 4.5287 2.6676 Entrance pupil 11.0513 25.3144 75.1476 position Exit pupil −11.4768 −31.6472 −99.8114 position Front principal 13.9362 33.2959 99.8492 points position Back principal 37.8076 32.3683 12.0235 points position Single lens data Lens Initial surface element number Focal length 1 1 −69.2986 2 3 50.3333 3 5 42.7195 4 7 −7.1113 5 9 −15.8467 6 11 15.7790 7 13 7.5057 8 15 9.5156 9 17 −5.3467 10 20 −47.2491 11 22 18.2151 Zoom lens unit data Initial Overall Lens surface Focal length of Front principal Back principal unit No. length lens unit points position points position 1 1 35.53500 4.46660 0.95744 2.62125 2 7 −7.38792 5.12640 −0.01273 0.71601 3 13 10.21334 4.12050 −2.05831 0.06771 4 20 −47.24910 0.50000 1.07343 1.25927 5 22 18.21508 1.68640 0.66066 1.26673 Magnification of zoom lens unit Lens Initial Wide-angle Middle Telephoto unit surface No. limit position limit 1 1 0.00000 0.00000 0.00000 2 7 −0.28399 −0.39590 −0.88325 3 13 −0.56572 −1.19853 −1.46846 4 20 1.26345 1.28209 1.24347 5 22 0.64419 0.65885 0.76170

Numerical Example 5

The zoom lens system of Numerical Example 5 corresponds to Embodiment 5 shown in FIG. 13. Table 13 shows the surface data of the zoom lens system of Numerical Example 5. Table 14 shows the aspherical data. Table 15 shows various data.

TABLE 13 (Surface data) Surface number r d nd vd Object surface ∞  1 47.82760 0.75000 1.84666 23.8  2 28.21300 0.01000 1.56732 42.8  3 28.21300 3.27700 1.49700 81.6  4 −1107.87480 0.15000  5 25.29660 2.38300 1.72916 54.7  6 77.85170 Variable  7 64.54210 0.30000 1.88300 40.8  8 5.72810 2.90780  9 −28.89180 0.30000 1.78590 43.9 10 16.49550 0.41550 11 11.41710 1.41500 1.94595 18.0 12 54.34020 Variable 13 6.03730 3.32960 1.49700 81.6 14 −48.63350 0.93260 15* 12.17690 3.24180 1.80470 41.0 16 −40.55760 0.01000 1.56732 42.8 17 −40.55760 0.40000 1.84666 23.8 18 7.33790 0.30000 19(Diaphragm) ∞ Variable 20* 10.70960 1.79450 1.52500 70.3 21* 682.87650 Variable 22 ∞ 0.78000 1.51680 64.2 23 ∞ (BF) Image surface ∞

TABLE 14 (Aspherical data) Surface No. 15 K = 0.00000E+00, A4 = −7.18404E−04, A6 = −2.38605E−05, A8 = −8.22730E−07 A10 = 0.00000E+00 Surface No. 20 K = 0.00000E+00, A4 = −1.44429E−04, A6 = 3.93254E−06, A8 = 3.07661E−07 A10 = −1.38658E−08 Surface No. 21 K = 0.00000E+00, A4 = −1.01717E−04, A6 = 2.13630E−06, A8 = 4.46802E−07 A10 = −1.80129E−08

TABLE 15 (Various data) Zooming ratio 13.97837 Wide-angle Middle Telephoto limit position limit Focal length 4.6500 17.4002 64.9995 F-number 3.58003 5.47052 6.27507 View angle 40.7265 12.6564 3.3680 Image height 3.5000 3.9020 3.9020 Overall length 51.3024 58.0531 68.9684 of lens system BF 0.90480 0.89076 0.84139 d6 0.3050 13.1596 25.0706 d12 19.0154 5.8493 1.3032 d19 5.3359 5.8777 14.8307 d21 3.0445 9.5789 4.2257 Entrance pupil 12.8525 47.1928 195.5208 position Exit pupil −11.9076 −19.4587 −57.9755 position Front principal 15.8148 49.7147 188.6883 points position Back principal 46.6524 40.6529 3.9688 points position Single lens data Lens Initial surface element number Focal length 1 1 −82.7025 2 3 55.4103 3 5 50.4274 4 7 −7.1360 5 9 −13.3223 6 11 15.0389 7 13 11.0291 8 15 11.9660 9 17 −7.3110 10 20 20.7050 Zoom lens unit data Initial Overall Lens surface Focal length of Front principal Back principal unit No. length lens unit points position points position 1 1 39.45012 6.57000 1.49757 3.93043 2 7 −6.77455 5.33830 0.19148 1.10718 3 13 11.56553 8.21400 −3.65554 1.57167 4 20 20.70503 1.79450 −0.01873 0.60013 Magnification of zoom lens unit Lens Initial Wide-angle Middle Telephoto unit surface No. limit position limit 1 1 0.00000 0.00000 0.00000 2 7 −0.22934 −0.40603 −1.41907 3 13 −0.70721 −2.63780 −1.72585 4 20 0.72674 0.41182 0.67275

The following Table 16 shows the corresponding values to the individual conditions in the zoom lens systems of the numerical examples.

TABLE 16 (Values corresponding to conditions) Numerical Example Condition 1 2 3 4 5 (1) f₁/f₂ −6.20 −5.40 −6.40 −4.81 −5.82 (a) f_(T)/f_(W) 14.71 11.03 16.47 9.39 13.98 (2) |f₁/f₄| 2.81 3.76 2.30 0.75 1.91 (3) L_(T)/f_(T) 0.96 1.08 0.96 1.28 1.06

The present disclosure is applicable to a digital input device such as a digital camera, a mobile terminal device such as a smart-phone, a Personal Digital Assistance, a surveillance camera in a surveillance system, a Web camera or a vehicle-mounted camera. In particular, the present disclosure is suitable for a photographing optical system where high image quality is desired like in a digital camera.

As described above, embodiments have been described as examples of art in the present disclosure. Thus, the attached drawings and detailed description have been provided.

Therefore, in order to illustrate the art, not only essential elements for solving the problems but also elements that are not necessary for solving the problems may be included in elements appearing in the attached drawings or in the detailed description. Therefore, such unnecessary elements should not be immediately determined as necessary elements because of their presence in the attached drawings or in the detailed description.

Further, since the embodiments described above are merely examples of the art in the present disclosure, it is understood that various modifications, replacements, additions, omissions, and the like can be performed in the scope of the claims or in an equivalent scope thereof. 

1. A zoom lens system, in order from an object side to an image side, comprising: a first lens unit having positive optical power; a second lens unit having negative optical power; a third lens unit having positive optical power; a fourth lens unit having optical power; and an aperture diaphragm provided between the third lens unit and the fourth lens unit, wherein in zooming from a wide-angle limit to a telephoto limit at the time of image taking, the first lens unit, the second lens unit, and the third lens unit are moved along an optical axis to perform magnification change, the third lens unit includes two or more lens elements, and one or more inter-lens-element air spaces, and the following conditions (1) and (a) are satisfied: −7.0<f ₁ /f ₂<−4.0  (1) f _(T) /f _(W)>9.0  (a) where, f₁ is a composite focal length of the first lens unit, f₂ is a composite focal length of the second lens unit, f_(W) is a focal length of the entire system at a wide-angle limit, and f_(T) is a focal length of the entire system at a telephoto limit.
 2. The zoom lens system as claimed in claim 1, wherein in zooming from a wide-angle limit to a telephoto limit at the time of image taking, the aperture diaphragm A moves along the optical axis, integrally with the third lens unit.
 3. The zoom lens system as claimed in claim 1, wherein the following condition (2) is satisfied: 0.5<|f ₁ /f ₄|<4.2  (2) where, f₁ is a composite focal length of the first lens unit, and f₄ is a composite focal length of the fourth lens unit.
 4. The zoom lens system as claimed in claim 1, wherein the following condition (3) is satisfied: 0.8<L _(T) /f _(T)<1.4  (3) where, L_(T) is an overall length of lens system (a distance from a most object side surface of the first lens unit to an image surface) at a telephoto limit, and f_(T) is a focal length of the entire system at a telephoto limit.
 5. The zoom lens system as claimed in claim 1, wherein the fourth lens unit has negative optical power.
 6. The zoom lens system as claimed in claim 1, wherein the fourth lens unit is composed of one lens element.
 7. The zoom lens system as claimed in claim 1, wherein a fifth lens unit having optical power is provided on the image side relative to the fourth lens unit.
 8. The zoom lens system as claimed in claim 7, wherein the fifth lens unit has positive optical power.
 9. The zoom lens system as claimed in claim 7, wherein the fifth lens unit is composed of one lens element.
 10. The zoom lens system as claimed in claim 7, wherein in focusing from an infinity in-focus condition to a close-object in-focus condition, the fourth lens unit or the fifth lens unit moves along the optical axis.
 11. An imaging device capable of outputting an optical image of an object as an electric image signal, comprising: a zoom lens system that forms the optical image of the object; and an image sensor that converts the optical image formed by the zoom lens system into the electric image signal, wherein the zoom lens system is a zoom lens system as claimed in claim
 1. 12. A camera for converting an optical image of an object into an electric image signal, and performing at least one of displaying and storing of the converted image signal, comprising: an imaging device including a zoom lens system that forms the optical image of the object, and an image sensor that converts the optical image formed by the zoom lens system into the electric image signal, wherein the zoom lens system is a zoom lens system as claimed in claim
 1. 